There are a number of procedures in which biological fluids such as blood, blood components as well as mixtures of blood or blood components with other fluids as well as any other liquid comprising biological cells, are managed. Examples of such procedures include treatments where blood is taken out in an extracorporeal blood circuit. Such treatments involve, for example, hemodialysis, hemofiltration, hemodiafiltration, plasmapheresis, blood component separation, blood oxygenation, etc. Normally, blood is removed from a blood vessel at a blood access and returned to the same blood vessel. During these procedures it is often desirable and also important to monitor the pressure in the biological fluid system.
US patent application 20020007137 describes a prior art dialysis pressure sensing system wherein the pressure in an extracorporeal blood circuit is measured with an ordinary pressure transducer.
Typically, when performing pressure sensing using arrangements according to prior art, the extracorporeal blood circuit is connected to a patient and a dialysis machine. The pressure sensor is located within the dialysis machine and operably and structurally connected to the extracorporeal blood circuit.
Even though the extracorporeal blood circuit typically is in the form of a disposable arrangement there is a risk of cross contamination between patients. Between the pressure sensor in the dialysis machine and the blood in the disposable extracorporeal circuit is arranged an air column in a connector line/column. The air column exerts a backpressure on the blood, thereby preventing blood from getting in contact with the pressure sensor/-machine. The dialysis machine normally comprises pumps of roller type creating a pulsating flow of blood in such a way that blood is penetrating into the connector line to some extent. In case the blood flow is blocked there is a potential risk that the backpressure exerted on the blood by the air column in the connector line is overcome and that blood reach a protective filter, protecting the pressure sensor. In such a case, cross contamination could occur if this situation reoccurs with another patient connected to the machine and the machine has not been cleaned properly. Also there is a potential risk that bacteria could grow in blood residuals at the protective filter.
Another problem is that of leakage, which may occur due to operator mistakes during set-up of the system. Needless to say, leakage could be of danger to an operator of the system in case contaminated blood is present in the system. Leakage may also lead to erroneous or less accurate pressure measurements.
International patent application with publication number WO 02/22187 discloses a blood pump having a disposable blood passage cartridge with integrated pressure sensors. Signal wires convey information from pressure transducers to a controller.
Hence, electrical contact problems may occur due to presence of spillage (or contamination) of fluids such as blood as well as contamination of particles such as salt crystals and burrs. Moreover electric connector means imply that there exist edges, indentations, protrusions etc. in the vicinity of means for transporting fluids, which typically enhances the risk of spillage (or contamination) of fluids as well as particles collecting in the area of the connector means. Needless to say, electrical connectors open to touch by operator, may also constitute an added risk of an operator being subject to electric shock.
Moreover, electric wiring and connectors that are needed for transmission of pressure information from pressure sensors according to prior art are unnecessarily complicated and adds to the risk of mistakes during use.
Thus, there is a general problem of how to provide a disposable fluid arrangement which is electrically safe, avoids risks relating to accumulation of spillage (or contamination) of fluids as well as particles, is easy to set-up, avoid leakage and which reduces the risk of cross contamination between patients and/or operators of the system.